Step 1: Understanding the Concept:
Atomic radius is defined as the typical distance from the center of the nucleus to the boundary of the surrounding shells of electrons.
The size of an atom is governed by periodic trends across periods and groups in the periodic table.
Step 2: Key Formula or Approach:
The approach is to use periodic trends, specifically the variation of effective nuclear charge (\(Z_{\text{eff}}\)) across a period.
As \(Z_{\text{eff}}\) increases, the atomic radius decreases.
Step 3: Detailed Explanation:
All the elements provided in the options (Boron, Carbon, Nitrogen, Oxygen, Fluorine) belong to the second period of the periodic table.
As we move from left to right across a period, electrons are sequentially added to the same principal energy shell.
Simultaneously, protons are added to the nucleus, which increases the nuclear charge.
Because electrons in the same shell do not shield each other very effectively, the effective nuclear charge (\(Z_{\text{eff}}\)) increases from left to right.
This stronger pull from the nucleus draws the electron cloud closer, leading to a decrease in atomic radius.
The order of elements from left to right is B, C, N, O, F.
Therefore, the atomic radius progressively decreases in the order: B > C > N > O > F.
Step 4: Final Answer:
Fluorine (F), being the rightmost element among the choices, has the least atomic radius.